The present invention relates to an exhaust gas system with circulation heat pipe.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
The operation of internal combustion engines, for example Otto or diesel engines requires combustible fuels. Due to limited oil reserves it is sought to maximize the efficiency of an internal combustion engine and with this the use of the energy contained in the combustible fuel. Due to the Carnot process however, the efficiency of an internal combustion engine for converting the energy contained in the combustible fuel is limited to about 40%.
This means that about ⅔ of the energy bound in the combustible fuel is not used for the actual purpose of the internal combustion engine, i.e. the conversion of chemical energy into mechanical energy but rather is lost as waste energy. In order to nevertheless use this energy, multiple approaches are currently taken in particular in the field of motor vehicles, for example to recover the heat energy or the energy bound in the exhaust gas and to use it in a respective application.
For example, the heat energy is used for heating the passenger compartment of the motor vehicle. In addition, there are also approaches in which thermoelectric generators convert the heat energy contained in the exhaust gas into electrical energy, which in turn can be used for operating a motor vehicle.
In order for an internal combustion engine to operate in an optimal efficiency spectrum, optimal operating conditions have to be established. The internal combustion engine which is predominantly manufactured from metallic materials is configured so that it operates within a good efficiency range at operating temperature. This means the different thermal expansions of the engine block, piston, piston rings, cylinder head, valves and further components are adjusted to one another so that they reach an optimal efficiency at an average operating temperature of the core components of about 90 to 100° C., and at this operating temperature the engine power is maximized and the load change is optimized. Also, the operating media of an internal combustion engine, for example the motor oil as well as transmission oils are optimized for use at the respective operating temperature.
Especially in the cold start phases which can take place at a temperature of 20° C., but which can also occur at starting temperatures of 0° C. or temperatures below zero, it is therefore necessary to quickly reach operating temperatures for the individual components.
For this, approaches are known from the state of the art, to withdraw heat from the exhaust gas by exhaust gas heat regeneration and to supply this heat to the site of use. This however, requires heat exchangers in the exhaust gas system which cause an increased exhaust gas counter pressure and thus lower the overall efficiency of the internal combustion engine.
Because of increasing demands to minimize exhaust gas emissions and the associated components for after treatment of the exhaust gases, for example a particle filter or a catalytic converter, it is contra productive to withdraw heat from the exhaust gas in the cold-start phase, because the components for after treatment of the exhaust gases also require energy in order to be fully effective. In addition, a heat transfer medium, in particular water, is used whose efficiency itself is limited and only offers a suboptimal solution.
DE 10 2009 049 196 A1 for example discloses a heat transfer device, in which heat is transported from a heat source to a heat sink in a targeted manner via a heat pipe. Further, the heat transport is controllable.
The afore mentioned state of the art however does not solve the problem to supply heat energy especially in the cold start phase to the desired heat sinks, without withdrawing too much energy from the exhaust in this phase and without increasing the exhaust counter pressure.
It would therefore be desirable and advantageous to provide an improved exhaust gas system with which a targeted heat transport is possible without withdrawing too much energy from the exhaust gas in defined operating situations.